libs/ical/Util/ComponentUtil.php

<?php

/*
 * This file is part of the eluceo/iCal package.
 *
 * (c) Markus Poerschke <markus@eluceo.de>
 *
 * This source file is subject to the MIT license that is bundled
 * with this source code in the file LICENSE.
 */

namespace Eluceo\iCal\Util;

class ComponentUtil
{
    /**
     * Folds a single line.
     *
     * According to RFC 5545, all lines longer than 75 characters should be folded
     *
     * @see https://tools.ietf.org/html/rfc5545#section-5
     * @see https://tools.ietf.org/html/rfc5545#section-3.1
     *
     * @param string $string
     *
     * @return array
     */
    public static function fold($string)
    {
        $lines = [];

        if (function_exists('mb_strcut')) {
            while (strlen($string) > 0) {
                if (strlen($string) > 75) {
                    $lines[] = mb_strcut($string, 0, 75, 'utf-8');
                    $string = ' ' . mb_strcut($string, 75, strlen($string), 'utf-8');
                } else {
                    $lines[] = $string;
                    $string = '';
                    break;
                }
            }
        } else {
            $array = preg_split('/(?<!^)(?!$)/u', $string);
            $line = '';
            $lineNo = 0;
            foreach ($array as $char) {
                $charLen = strlen($char);
                $lineLen = strlen($line);
                if ($lineLen + $charLen > 75) {
                    $line = ' ' . $char;
                    ++$lineNo;
                } else {
                    $line .= $char;
                }
                $lines[$lineNo] = $line;
            }
        }

        return $lines;
    }
}